Microspheres with regular and ordered surface patterns (patches) have tremendous potential for usage in sensor, biomedical and photonic applications. However a method for the easy patterning of the microsphere surface, post pattern functionalization and the easy recovery of the microspheres is not currently available.
Several attempts to synthesize patchy microspheres have been explored. Further, more complex methods have been used to reduce the size of the patches (from Janus to discrete patches separated by some distance). However, these procedures have thus far only patterned one of the particle hemispheres. Furthermore, most of these techniques (including ones that can affect the entire particle surface) are not suitable for post pattern functionalization using soft structures like proteins or polymers.
Recently, Wang et al., Angew. Chem. Int. Ed. 2008, 47, 4725-4728, has reported self-assembly mediated packing of the microparticles. They were further annealed at the contact points to generate non-spherical particles. The major disadvantage with this approach is that the surface chemistry at the contact point is altered due to annealing. On the other hand Snyder, C. E.; Yake, A. M.; Feick, J. D.; Velegol, D. Langmuir 2005, 21, 4813-4815 proposed a more robust technique, based on “microparticle lithography”. The disadvantage with this technique is that it can be done only in batches and the formed patterns are not in a regular order. Scaffolding and treatments in microfluidic chamber are possible alternatives. However, special care will need to be taken in recovery of the particles with high surface fidelity.